Enlightenment:
If you believe in Him by calling on His name, it is proof that you have received Him. And since you have received Him, you have received the authority to become a child of God. What is this authority? It is Christ Himself as life to you. Christ as life is simply the Spirit of sonship, and this Spirit of sonship makes you God’s child. You can know that you are a child of God by two things: by the fact that you believe in Him and call on His name, and by the fact that, at times, you spontaneously and sweetly cry, “Abba, Father.” If you can call God “Abba, Father” in such a sweet way, it proves that you are His child.
As verse 13 declares, this birth is not of blood, nor of the will of the flesh, nor of the will of man. Blood (Gk., bloods) here signifies the physical life; the will of the flesh denotes the will of fallen man after man became flesh; the will of man refers to the will of man created by God. When we became a child of God, we were not born of our physical life, our fallen life, or our created life—we were born of God, the uncreated life. For human beings to become children of God is for man to have the divine life and the divine nature.
The birth described in these verses is not the natural birth which we had through our parents; it is the second birth which occurred when we believed in the name of the Lord Jesus.